To evaluate factors involved in the regulation of the performance of the heart and peripheral circulation. Specifically, this involves evaluating the relative contribution of a number of factors including neural reflexes from arterial baroreceptors, cardiopulmonary receptors and autoregulation. Animal models include conscious dogs and anesthetized rabbits. Studies include the identification of neural pathways regulating the cardiovascular response to acute myocardial ischemia and the interaction of reflexes arising from the cardiopulomonary and arterial baroreceptors.